For those new to shooting you hear the term MOA used a lot. “I have a gun that shoots .5 MOA groups”. “My scope adjusts in 1/4 MOA clicks”. Statements like that can lead to people asking what is MOA? MOA stands for Minute of Angle and is based on the angular measurement minute of arc or 1/60 of one degree.
Minute of Angle is used to measure the average point of impact of a bullet on target, as bullets fired from a gun will impact in a cone-shaped trajectory. The farther they go before they hit, the more likely they are to hit the target within a bigger circle. No matter what the bullet ballistics of the bullet they will all hit within a circle of impact known as MOA. Of course, the accuracy of the gun greatly affects the size of this circle.
Why is MOA used?
The Human Eye sees in a visual angle. The closer you are to an object the less of it you can see. However, the farther away from it the more of it you can see. The size of the object doesn’t change but your visual angle does. It’s the same when you are aiming a rifle the farther away you are from your target the smaller it appears.
The problem arises when you try to measure how far off your point of impact is versus your point of aim on your target. This is all assuming you followed all the shooting fundamentals and you hit where you were aiming.
We can’t use inches since we have an angular vision, and since rifles shoot in a cone shape trajectory, which means we must use degrees.
Let’s say you adjusted your rifle scope crosshairs in whole degrees. The problem with this would be that even a 1-degree angle change from the center of your scope would translate into 60 inches at 100 yards, and it would get worse the farther you go out. At 200 yards that same 1-degree measurement would equal 120 inches. You can see very quickly that you need a measurement that is much smaller than even 1 degree. Lucky for us Minute of Angle fits that measurement. Since MOA is equal to 1/60 of a degree.
Minute Of Angle and the math
Without going into lots of complicated math formulas, 1 MOA is equal to roughly a 1″ circle at 100 yards. I say roughly because the actual math says it’s equal to 1.047 inches. The difference between using 1″ for every 100 yards and 1.047″ for every 100 yards is only .47″ at 1000 yards.
As a result, using 1″ per 100 yards for this is perfect for most people as there is not enough difference to matter. So unless you are a long-distance shooter trying to adjust for windage, and bullet drop at 1000 yards or longer the difference between mathematical Minute of Angle and the standard shooters’ definition of Minute of Angle doesn’t matter at all.
Converting MOA to Inches
Knowing that 1 MOA is equal to 1″ at 100 yards you can now figure out how many MOA is equal to inches at any distance. The math on this is fairly simple. To convert Minute of Angle to inches at any distance, all you do is take you distance times your MOA divided by 100, and this will equal inches at your set distance. This can be confusing so let’s give a few examples:
4 MOA at 300 yards (4*300)/100 = 12 so 4 MOA is equal to 12″ at 300 yards
3 MOA at 200 yards (3*200)/100 = 6 so 3 MOA is equal to 6″ at 200 yards
2 MOA at 100 Yards (2*100)/100 = 2 so 2 MOA is equal to 2″ at 100 yards
The math works with and distance and any MOA measurement. It even works for distances under 100 yards. So let’s say 1 MOA at 25 yards. Take 25*1=25/100 equals 1/4″. It’s really that simple. Understanding this comes in handy for all sorts of things.
Converting Inches to MOA
Converting inches to MOA is just as simple as converting MOA to inches. It’s just in reverse. So as an example:
2″ at 100 yards is equal to 2 MOA. It works like this (2″/100)*100=2
4″ at 400 yards is equal to 1 MOA (4″/400)*100=1
6″ at 250 yards is equal to 2.4 MOA (6/250)*100=2.4
Rifles Scopes and MOA
The most common use of Minute of Angle is sighting in a rifle scope. Many Rifle Scopes are adjusted based on MOA. When adjusting a rifle scope, you will read the amount of adjustment per click labeled on the scope. It’s common for a scope to say 1/4 MOA = 1 Click.
With the knowledge of how Minute of Angle works all that needs done to sight a scope in is measure how far from the point of impact your shots are from the point of aim. Then turn each scope adjustment the correct amount of clicks.
As an example, you have a group of 3 shots that are hitting 2″ high and 4″ to the left of the where you were aiming, while shooting at 100 yards. This means you are 2 MOA high and 4 MOA to the left, with each click equal to 1/4 MOA. You can turn your elevation adjustment down 8 clicks and to the right 16 clicks. What this means is that if you were to lock your rifle down and shot one shot, you could adjust your scope and the next shot will be dead on. Unfortunately, it’s not that easy when you take into account your shooting ability and the accuracy of the rifle.
Rifles and MOA accuracy
Many people use Minute of Angle to describe the accuracy of their rifles. By using a standard measurement it’s easy to see how one gun’s accuracy is compared to another. You don’t even have to shoot each one at the same distance to understand which firearm is more accurate. Granted some calibers are more accurate at longer distances. You can still compare it to calibers that are better at closer ranges.
Any rifle that can shoot an average group of 3 to 5 shots within a 1″ group at 100 yards is considered accurate. Better known as a 1 MOA rifle. Many of the high dollar rifles shoot sub-MOA groups.
What Affects Rifle Accuracy
There are plenty of things that affect the accuracy of a rifle:
- The Shooter’s ability
- Barrel Quality
- Action and trigger
- Stock
- Sights
- Ammo quality
These are just a few examples of things that affect the accuracy of a rifle. Just like the shooting fundamentals teach you how to shoot the exact same way for every shot. The gun itself needs to shoot the exact same way each time you pull the trigger. A thin lightweight barrel can heat up after a few shots and change the bullet trajectory, a rough trigger can cause the firing pin the be released at a different point each trigger pull. Having a sloppy action or a loose stock can change things also. Not to mention scope rings that aren’t tight or ammo that doesn’t have a consistent powder charge. All of these can affect the accuracy of any gun.
Conclusion
Minute of Angle is a measurement equal to 1/60th of 1 degree used for many different things in the shooting world. From sighting in a rifle to comparing the accuracy of a rifle. It’s a measurement used to help shooters out when measuring windage and elevation at various distances.
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